| 摘要 |
PURPOSE:To provide overwrite S/N at about the same degree in the inside and outside circumferential parts of a disk and to permit recording of signals at high density to the disk by making the thickness of the medium in the outside circumferential part smaller than the thickness of the medium in the inside circumferential part. CONSTITUTION:The medium is formed to have the thickness smaller in the outside circumferential part than in the inside circumferential part. For example, a substrate 1 is a disk which has about 130mmphi outside diameter and 40mmphi inside diameter and is formed by subjecting the surface of Al having 1.9mm thickness to NiP plating to 50mum thickness. Co-20wt% Cr alloy is deposited thereon. The Co-Cr alloy 2 is a vertically magnetizable recording medium and permits recording and reproduction to the high density. The Co-Cr medium is formed to have 0.5mum thickness on the innermost circumference and 0.35mum thickness on the outermost circumference and in this manner the thickness on the outermost circumference is made smallest. Such distribution is obtainable by changing adequately the spacing between a sputter target and the substrate in the stage of sputtering the Co-Cr alloy.
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